Human Health Risk Assessment

Introduction

A human health risk assessment is the process to estimate the nature and probability of adverse health effects in humans who may be exposed to chemicals in contaminated environmental media, now or in the future.

To explain this better, a human health risk assessment addresses questions such as:

What types of health problems may be caused by environmental stressors such as chemicals and radiation?

What is the chance that people will experience health problems when exposed to different levels of environmental stressors?

Is there a level below which some chemicals don't pose a human health risk?

What environmental stressors are people exposed to and at what levels and for how long?

Are some people more likely to be susceptible to environmental stressors because of factors such as age, genetics, pre-existing health conditions, ethnic practices, gender, etc.?

Are some people more likely to be exposed to environmental stressors because of factors such as where they work, where they play, what they like to eat, etc.?

The answers to these types of questions helps decision makers, whether they are parents or public officials, understand the possible human health risks from environmental media.

Why does EPA evaluate whether children may be at greater health risks than adults?

Almost 500 years ago Paracelsus (1493-1541) wrote: "Dosis facit venenum" or "the dose makes the poison." The relationship between dose and response (health effect) is still one of the most fundamental concepts of toxicology - or is it? For pollutants that act as developmental toxicants, the same dose that may pose little or no risk to an adult can cause drastic effects in a developing fetus or a child. Methyl mercury is but one example of a chemical that is much more toxic early in life. Scientists have become increasingly aware that children may be more vulnerable to environmental exposures than adults because:

their bodily systems are developing;

they eat more, drink more, and breathe more in proportion to their body size; and

their behavior, such as crawling and hand-to-mouth activity, can expose them more to chemicals and microorganisms.

In light of what is now known about the greater susceptibility early in life to some stressors, Executive Order 13045 -- Protection of Children from Environmental Health Risks and Safety Risks -- was issued in 1997. This Executive Order directs that all federal agencies, including EPA, shall make it a high priority to identify and assess environmental health risks and safety risks that may disproportionately affect children; and shall ensure that their policies, programs, activities, and standards address disproportionate risks to children that result from environmental health risks or safety risks.